This-relates generally to imaging devices, and more particularly, to imaging devices that measure the flight time of reflected light pulses.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. In a typical arrangement, an electronic device is provided with an image sensor and a corresponding lens. Some electronic devices use arrays of image sensors and corresponding lenses to gather image data. This type of system, which is sometimes referred to as an array camera, may be used to capture depth information from a scene using a parallax effect based on a known physical offset between image sensors.
Depth information such as information about the distance of an object from an electronic device is also commonly captured using a dedicated range finder such as a radar system. In a typical range finder, light of a known frequency is emitted from the range finder in the direction of an object and is reflected off of the object in the direction of the range finder. Range finders typically have a light sensor that detects the reflected light. Distance information is then determined based on the time-of-flight of the light between the emission and detection of the light and the known speed of light.
Time-of-flight distance information is also sometimes extracted by a range finder from an emitted and reflected pulse of light by synchronizing the emission and the detection of the light. The light sensor is often configured to collect light for a predetermined amount of time alter the emission of the light. Light reflected from a far away object may not return during the light collection period while light reflected from a nearby object may return and be collected during the light collection period. This is because the light reflected from the far away object travels a longer distance and therefore has a longer time-of-flight. However, reflected intensity of emitted light most often is very small compared to natural background scenery intensity. Oftentimes the intrinsic brightness of objects in a typical real-world scene is hundreds or thousands of times more intense than the brightness of the reflected emitter-light pulse. Difficulties that arise in separating background intensity from reflected light pulse intensity can therefore be problematic when capturing images with depth information. In an effort to reduce background interference, some imaging devices operate only in the infrared (IR) range utilizing IR emitters and narrow band IR filters. Operating only in the IR range, however, prevents an imaging device from producing any color information.
It would therefore be desirable to be able to provide improved imaging devices for capturing depth information and color image at the same time.